2003A&A...405.1043Z

We have conducted a survey of FUSE spectra of 235 Galactic B-type stars in order to determine the boundaries in the H-R diagram for the production of the superion OVI in their winds. By comparing the locations and morphology of otherwise unidentified absorption features in the vicinity of the OVI resonance doublet with the bona fide wind profiles seen in archival IUE spectra of the resonance lines of NV, SiIV and CIV, we were able to detect blueshifted OVI lines in the spectra of giant and supergiant stars with temperature classes as late as B1. No features attributable to OVI were detected in dwarfs later than B0, or in stars of any luminosity class later than B1, although our ability to recognize weak absorption features in these stars is severely restricted by blending with photospheric and interstellar features. We discuss evidence that the ratio of the ion fractions of OVI and NV is substantially different in the winds of early B-type stars than O-type stars.